Rose Hilridge (the bounty hunter)'s gun is a Smith & Wesson Military & Police Model (.38 special) double action revolver. The M&P wasn't initially developed until 1899 and her model is an early 20th century variant. In fact most of the handguns are too modern for the time period. Only some Colt 1873 Single Action Army revolvers seen in the background (that are never fired) are not anachronistic to 1892.